The major objective of the overall research program is to examine the neurobiological consequences of aging that distinguish rats with cognitive impairment from the unimpaired aged cohorts and to determine the causes of these changes in the brain. Toward this goal the Animal Resource will serve all of the research projects by maintaining a colony of pathogen-free male Long-Evans rats, which are additionally screened for disability and physiological impairment. All rats in the Animal Resource undergo assessment of cognitive function in a standardized protocol fort "place" and "cue" learning in a water maze apparatus. Additional behavioral testing in this core will occur as specified for individual projects. Material from animals in the resource is then provided to the projects, in a form appropriate to the methods used in the neurobiological studies (sacrifice/perfusion/dissection). In some instances lie animals will be transferred from the Resource to projects for further in vivo analysis (i.e., electrophysiological recording) or to provide fresh tissue as needed for in vitro studies. The Animal Resource Core will provide all behavioral data it acquires to the Data Management Core for analysis and data archive.